An improved pipe liner and associated methods, including a method of manufacturing the improved pipe liner and a method of lining a host pipe with such a pipe liner. The invention solves the problem of gas permeation through a polymer liner in hydrocarbon service which can result in corrosion of the host pipe and can also cause liner collapse. Corrosion occurs due to contact between corrosive species and the host pipe itself. Gases (307) can also accumulate in an annulus between or within the liner (305) and the host pipe (303) and expand during operational de-pressurisation of the pipeline, causing collapse of the liner. The improved pipe liner comprises a barrier layer (311), which prevents permeation through the liner, surrounding an inner polymer pipe (305A) and optionally covered by an outer polymer pipe (305B). The inner polymer pipe is porous which permits free movement of gas between the internal bore (302) of a lined pipe and the barrier layer, so as to prevent accumulation of gases anywhere in the lined pipe, while ensuring that gases do not permeate to, and damage, the host pipe. The liner can be inserted using Swagelining, roll-down, or any other suitable close-fit lining techniques, without compromising the effectiveness of the barrier layer.